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TRL Calibration check

Question asked by vysakh@tcs30 on Jul 27, 2011
Latest reply on Jul 27, 2011 by vysakh@tcs30

I am performing a TRL calibration using 50GHz E8364B PNA. Normally, to check for a good calibration i follow the steps below.

1. Check the insertion loss of the THRU ( reference standard ) and make sure mag(S21) = 0 across the frequency range of interest.
2. Check a known SHORT or OPEN standard from the calibration kit and plot it in Smith's chart.

Are these simple steps good enough to see my calibration is good or not ? If then i have another question.

I performed a TRL cal on Day 1 and i need to use the same cal on Day 2 ( around 20 hours in my case) . I check the "THRU" reference standard on Day 2 before the measurements and check for the difference from Day 1. Is a magnitude of less than 0.1dB good enough or a phase difference of 1 deg good ?

Or does everything depends on what level of accuracy i need in my measurements?  Attached are the THRU reference plots from my calibration on Day 1 ( Blue ) and same calibration on Day 2 (Red ).

Thanks in advance.

Vysakh Sivarajan
Signal Integrity Engineer